A quantum network is a communication system that uses the quantum properties of light particles (photons) to transmit information between connected devices. Instead of encoding data as simple on-or-off electrical signals like today’s internet, a quantum network encodes information in the polarization and quantum states of individual photons. This enables capabilities that are physically impossible on classical networks, including communication that reveals any attempt at eavesdropping and the ability to link distant quantum computers into a single, more powerful system.
How Quantum Networks Differ From Classical Ones
The internet you use every day sends packets of information as classical signals: bursts of light through fiber-optic cables, electrical pulses through copper wire, or microwaves for wireless connections. Each signal represents either a 0 or a 1. A quantum network also uses photons traveling through fiber or open air, but it exploits three quantum phenomena that classical networks cannot access: superposition, no-cloning, and entanglement.
Superposition means a photon can represent 0 and 1 simultaneously until it’s measured. No-cloning means it’s physically impossible to make a perfect copy of an unknown quantum state, which turns out to be a powerful security feature. Entanglement is the strangest property of all: two photons can be linked so that measuring one instantly determines the state of the other, regardless of the distance between them. These three properties together are what make quantum networking fundamentally different, not just a faster version of what already exists.
Moving Information With Entanglement
In a classical network, you copy data and send the copy. In a quantum network, copying is forbidden by the laws of physics, so information moves through a process called quantum teleportation. Despite the name, nothing travels faster than light. Instead, two nodes share a pair of entangled photons in advance. When the sender performs a specific measurement on their photon alongside the data they want to transmit, the receiver’s entangled photon instantly reflects the change. The sender then sends two ordinary bits of classical information (a quick message saying which measurement result they got), and the receiver uses that to reconstruct the original quantum state.
In 2022, a team published results in Nature demonstrating teleportation between nodes that weren’t even directly connected. Their network had three nodes, each built around a diamond-based quantum processor. The middle node acted as a relay: it established entanglement with both outer nodes, then performed an “entanglement swap” that linked the two endpoints together. Once that link existed, data could be teleported from one end to the other, passing through the middle node without that node ever learning what was sent. This relay process is the foundation of how larger quantum networks will eventually operate.
Unbreakable Encryption
The most mature application of quantum networking is quantum key distribution, or QKD. In the most widely studied version, the sender encodes random bits as polarized photons, choosing randomly between two different polarization schemes. The receiver independently picks which scheme to measure with. Afterward, both sides publicly compare which measurement scheme they used for each photon (but not the results). They keep only the bits where they happened to use the same scheme, discarding the rest. This shared set of matching bits becomes their encryption key.
The security comes from quantum physics itself. If someone intercepts a photon to read it, the measurement disturbs its quantum state in a detectable way. The sender and receiver can check a subset of their shared key for errors. If the error rate is higher than expected, they know someone tampered with the channel and can discard that key. No amount of computing power, quantum or otherwise, can defeat this protection because it’s based on physical law rather than mathematical difficulty.
This has already moved beyond the lab. China operates a 2,000 km terrestrial fiber-based quantum network connecting 32 nodes across major cities from Beijing to Shanghai. In 2025, scientists reported establishing an ultra-secure quantum satellite link spanning 12,900 km between continents, building on earlier work with the Micius quantum satellite that demonstrated a 7,600 km link between China and Austria in 2017.
Linking Quantum Computers Together
Individual quantum computers are currently limited in the number of qubits they can reliably operate. Distributed quantum computing uses a quantum network to connect multiple smaller quantum processors so they function as one larger system. Photons traveling through the network carry entanglement between processors, enabling operations across machines without physically moving qubits between them.
The technique that makes this work is called quantum gate teleportation. It uses one shared entangled pair and two classical bits to perform a computational operation between qubits in separate machines. Combined with operations each machine can do internally, this provides a complete set of tools for any quantum computation. The network’s layout can be reconfigured dynamically without opening the complex cooling or vacuum systems that house the processors, and the approach works across different hardware platforms, including trapped ions, diamond-based systems, and neutral atoms.
Fiber, Satellites, and the Distance Problem
Quantum networks today use two main channels: fiber-optic cables and free-space links (typically satellite-to-ground). Each has tradeoffs. Fiber cables lose about 0.2 decibels of signal per kilometer at standard telecom wavelengths. That sounds small, but it compounds: after 150 km, you’ve lost 30 dB, meaning only one in a thousand photons makes it through. Free-space transmission follows the inverse-square law of laser diffraction, which means losses grow more slowly with distance. At longer ranges, satellite links have a clear advantage over fiber.
Satellites can bridge continents, but they require clear line-of-sight and are affected by atmospheric conditions. Fiber is reliable and already installed worldwide, but distance limits it without some way to boost the signal. The practical quantum networks being built today combine both: fiber for metropolitan-scale connections and satellites for long-haul links.
Quantum Repeaters and Memory
Classical internet repeaters simply copy a weakening signal and retransmit it at full strength. Quantum networks can’t do this because quantum states cannot be perfectly copied. Quantum repeaters instead work by breaking a long link into shorter segments, generating entanglement over each segment independently, and then stitching those segments together through entanglement swapping at each relay point.
This process requires quantum memory: a device that can hold a fragile quantum state long enough for the next segment to complete its entanglement. The challenge is efficiently moving quantum information into and out of the physical material used for storage. Trapped ions currently offer the longest storage times, with quantum memory lifetimes exceeding 30 minutes and very low error rates per swap operation. Atomic ensembles using a technique called electromagnetically induced transparency can store photons for shorter periods but offer different practical advantages. Arrays of neutral atoms show promise for improving how efficiently memory systems interface with light compared to conventional designs.
The Biggest Obstacle: Decoherence
Quantum states are extraordinarily fragile. Interactions with the surrounding environment, even stray heat or vibration, cause qubits to lose their quantum properties in a process called decoherence. This is the single largest barrier to building a global quantum network. A qubit that decoheres mid-transmission ends up in an undetermined state, and the information it carried is lost.
Two main strategies address this. Quantum error correction codes add extra qubits that encode the same information redundantly, so the system can detect and fix errors without directly measuring (and destroying) the data qubits. Entanglement distillation takes multiple imperfect entangled pairs and combines them to produce fewer, higher-quality pairs. Both techniques work, but they require additional qubits and processing at every stage, which is part of why scaling quantum networks remains difficult.
Architecture of a Quantum Internet
Engineers are designing quantum networks with a layered architecture inspired by the TCP/IP model that runs today’s internet. The current blueprint has five layers, each handling a different job. The physical layer manages the actual hardware connections between nodes. The link layer generates reliable entanglement between neighboring nodes, using error-mitigation techniques to suppress losses. The network layer handles routing, choosing which path through the network to use for building end-to-end entanglement and deciding where to perform purification along the way.
Above those, the transport layer provides the end-to-end service that applications actually use, delivering high-quality entangled pairs between distant nodes via teleportation. Finally, the application layer provides the interfaces that users and software interact with, where they can specify requirements like how pure the entanglement needs to be and how fast pairs need to be generated. This layered approach means that, just like today’s internet, different hardware and different applications can work together through shared protocols without needing to know each other’s details.